1. Field of the Invention
The present invention generally relates to fusers and image forming apparatuses, and particularly relates to a fuser which is provided with an electricity storage device for supplying power to a heating unit, and to an image forming apparatus having such a fuser provided therein.
2. Description of the Related Art
In image forming apparatuses such as copiers, printers, and facsimile machines, generally, a toner image is first formed on a sheet such as transfer paper by use of electrophotography, and is then fused with the sheet by heat applied by a fuser.
The fuser heats up a roller, a loop belt, or the like by heat generated by a heating unit responsive to power supply, and brings a fusing member comprised of the roller, the loop belt, or the like in contact with the sheet so as to heat the toner. Power supply to the heating unit has conventionally been a commercial AC power supply. In recent years, fusers that supply power to a heating unit by simultaneous use of an electricity storage device have also been developed (e.g., Japanese Patent Application Publication No. 2002-174988, paragraphs 0035–0041, FIG. 5).
When the fuser is activated from a standby state by switching on of main power supply, there is a need to shorten a wait period that passes before the apparatus becomes usable. In consideration of this, a plurality of heating units receive power from a commercial AC power supply and an electricity storage device, respectively, to heat up the fuser member. This makes it possible to rapidly raise temperature up to a level sufficient for the fusion of toner (i.e., reload temperature).
The related-art fusers have a drawback in that a switch for supplying power from an electricity storage device to a heating unit has a short operating life. Moreover, the heating unit that receives power supply from the electricity storage device also has a short operating life. These factors make it difficult to provide a fuser unit that is maintenance free.
Accordingly, there is a need for a fuser that supplies power from an electricity storage device to a heating unit and is maintenance free because of an extended operating life of a switch and a heating unit, and, also, there is a need for an image forming apparatus having such a fuser provided therein.